"And you must also remember," continued the doctor, "that the brighter the light the darker will be the shadow. Now, this projectile is a perfectly black, non-reflecting object five feet wide. It will cast a shadow in front of it five hundred feet long. When we are comparatively near Mars my telescope, situated in the miniature night cast by the projectile, will find the planet, and we can then steer directly for him. If we should chance within eighty thousand miles of him, he would attract us to him in a straight line. But we shall not rely upon chance. Moreover, when we are as near to him as that, the light and heat of the Sun's rays will have decreased sixty or seventy per cent. When Mars is farthest from the Sun, he receives only one-third as much light as the Earth does. But he is now almost at his nearest point to the Sun, and receives half as much light."
"Well, you certainly have a pretty clear idea of how to steer the course all the way, Doctor. And I was hasty enough to think you had overlooked this entire phase of the subject!" I ejaculated.
"Indeed, I have thought of it very much. And we should not enjoy all these advantages if we had not started just before opposition. At any other time the Earth's shadow would not point toward Mars, nor would the transit of the Earth over the Sun be of any use to us."
"All this reassures me greatly," I replied; "but I shall keep a close watch from my rear window for danger lights on the Earth."
"It must be time for breakfast," put in the doctor. "Will you see how tempting a meal you can prepare?"
There was one reservoir built inside the compartments, from which we drew cool water, and another built next to the outer steel framework, from which we could draw boiling water. As this tank was connected with the discharge pipe of the air-pump, and thus with the exterior, I was disgusted to find that, although the water boiled furiously, and was rapidly wasting away in steam, it did not become hot enough to make good beef tea. The heat escaped with the steam at a comparatively low temperature, so that I was compelled to boil water over my gas jet for the meat extract, which we drank instead of coffee. I also prepared some sandwiches of roast beef and cold ham, and with great relish we began our diet of ready cooked foods, which was to continue for so long.
After this meal I felt quite sleepy, for I had enjoyed but three hours' rest. The doctor saw my yawns and told me to turn out the gas and have a long doze, and I was glad enough to do so.
I must have slept soundly for an hour or two, and then I remember dozing and rolling lazily in my bed, as I usually did at home on Sunday mornings. During my previous nap the bunk had seemed hard and cramped, and I had privately grumbled at the doctor for overlooking personal comforts; but now I felt that luxurious sensation of sleeping on soft mattresses and yielding springs, though of course I had neither. I do not know how soon I should have thoroughly awakened had I not lifted my hand to rub my eye, and unwittingly dealt myself a stinging blow in the face. This roused me.
But what was the matter with that arm? It was as it had once been in a nightmare, when it felt detached from its place, and moved lightly and without effort, like a bough in the wind. I pinched it with my other hand, and it was quite sensible to the pain. In fact, the other arm was now acting in the same queer way. I arose in bed quickly to see what was the matter, and the upper part of my body bent violently over and struck against my knees. Then my effort to take an upright position threw me on my back again. Evidently my muscles were not working as they were when I went to bed. They must be over-excited and over-active. I immediately thought of my heart as the principal and controlling muscle, and in my eagerness to feel its beating my hand dealt me a slap in the chest. These blows, though rapid, did not seem to hurt as much as they ought, after the first stinging sensation. I found my heart was beating regularly enough.
"Doctor!" I cried out presently, more to test my voice than for anything else. It sounded perfectly natural, and my vocal chords were not over-stimulated or abnormal.